The present invention relates to a novel process for preparing cyclocitral. More particularly, it relates to a process for preparing cyclocitral from pyronene. The cyclocitral obtained constitutes an intermediate in the synthesis of vitamin A and may thus be used for this purpose.
A method for preparing cyclocitral from an unsaturated ketone involving the formation of an epoxide intermediate by means of a sulphur ylide is known in the prior art (Rosenberger et al., Helvetica Chemica Acta, Vol. 63, Fasc. 6 (1980)).
However, the starting ketone (trimethylcyclohexenone) is an expensive product and is difficult to obtain. This has effectively prevented industrial exploitation of the process.
Cyclocitral may also be prepared by cyclization of citralanil and hydrolysis of the protective amine group (Henbest et al., J. Chem. Soc., 1154 (1952)). However, this method requires multiple steps and involves the use of aniline, a toxic product.
Nothing in these documents teaches or suggests the possibility of preparing cyclocitral from pyronene. The process of the invention constitutes a novel means of producing cyclocitral which is particularly efficient and permits the production of cyclocitral from inexpensive and easily obtainable starting materials.